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	$190.73	10.120%	$210.0319	$210.03	$210.05	$210.00
Purchase #2	$240.92	9.380%	$263.5183	$263.52	$263.50	$263.50
Purchase #3	$25.31	4.792%	$26.5229	$26.52	$26.50	$26.50
Purchase #4	$248.46	7.315%	$266.6348	$266.63	$266.65	$266.60
Purchase #5	$79.85	4.335%	$83.3115	$83.31	$83.30	$83.30
Purchase #6	$56.64	4.376%	$59.1186	$59.12	$59.10	$59.10
Purchase #7	$30.86	6.497%	$32.865	$32.87	$32.85	$32.90
7 purchase totals =	$872.77		$942.0030	$942.00	$941.95	$941.90