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	$185.64	3.403%	$191.9573	$191.96	$191.95	$192.00
Purchase #2	$76.86	10.751%	$85.1232	$85.12	$85.10	$85.10
Purchase #3	$62.71	3.478%	$64.8911	$64.89	$64.90	$64.90
Purchase #4	$53.95	9.581%	$59.1189	$59.12	$59.10	$59.10
Purchase #5	$225.59	12.406%	$253.5767	$253.58	$253.60	$253.60
Purchase #6	$97.97	10.453%	$108.2108	$108.21	$108.20	$108.20
Purchase #7	$227.60	6.496%	$242.3849	$242.38	$242.40	$242.40
7 purchase totals =	$930.32		$1,005.2629	$1,005.26	$1,005.25	$1,005.30