Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$105.55	5.712%	$111.579	$111.58	$111.60	$111.60
Purchase #2	$239.49	12.265%	$268.8634	$268.86	$268.85	$268.90
Purchase #3	$165.62	13.568%	$188.0913	$188.09	$188.10	$188.10
Purchase #4	$127.99	11.538%	$142.7575	$142.76	$142.75	$142.80
Purchase #5	$210.81	11.519%	$235.0932	$235.09	$235.10	$235.10
Purchase #6	$36.38	13.856%	$41.4208	$41.42	$41.40	$41.40
Purchase #7	$166.71	8.156%	$180.3069	$180.31	$180.30	$180.30
7 purchase totals =	$1,052.55		$1,168.1121	$1,168.11	$1,168.10	$1,168.20