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	$6.35	9.251%	$6.9374	$6.94	$6.95	$6.90
Purchase #2	$66.98	5.478%	$70.6492	$70.65	$70.65	$70.60
Purchase #3	$96.73	5.214%	$101.7735	$101.77	$101.75	$101.80
Purchase #4	$56.74	4.517%	$59.3029	$59.30	$59.30	$59.30
Purchase #5	$155.73	6.152%	$165.3105	$165.31	$165.30	$165.30
Purchase #6	$81.93	9.417%	$89.6453	$89.65	$89.65	$89.60
Purchase #7	$139.78	10.264%	$154.127	$154.13	$154.15	$154.10
7 purchase totals =	$604.24		$647.7458	$647.75	$647.75	$647.60