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	$174.46	9.363%	$190.7947	$190.79	$190.80	$190.80
Purchase #2	$95.32	8.372%	$103.3002	$103.30	$103.30	$103.30
Purchase #3	$90.29	9.386%	$98.7646	$98.76	$98.75	$98.80
Purchase #4	$166.67	11.111%	$185.1887	$185.19	$185.20	$185.20
Purchase #5	$48.97	3.372%	$50.6213	$50.62	$50.60	$50.60
Purchase #6	$245.71	8.228%	$265.927	$265.93	$265.95	$265.90
Purchase #7	$122.98	3.370%	$127.1244	$127.12	$127.10	$127.10
7 purchase totals =	$944.40		$1,021.7209	$1,021.71	$1,021.70	$1,021.70