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	$191.54	9.174%	$209.1119	$209.11	$209.10	$209.10
Purchase #2	$51.95	8.249%	$56.2354	$56.24	$56.25	$56.20
Purchase #3	$82.30	8.444%	$89.2494	$89.25	$89.25	$89.20
Purchase #4	$90.88	9.214%	$99.2537	$99.25	$99.25	$99.30
Purchase #5	$235.31	5.167%	$247.4685	$247.47	$247.45	$247.50
Purchase #6	$234.44	3.372%	$242.3453	$242.35	$242.35	$242.30
Purchase #7	$90.69	7.865%	$97.8228	$97.82	$97.80	$97.80
7 purchase totals =	$977.11		$1,041.4870	$1,041.49	$1,041.45	$1,041.40