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	$211.86	8.502%	$229.8723	$229.87	$229.85	$229.90
Purchase #2	$235.91	7.611%	$253.8651	$253.87	$253.85	$253.90
Purchase #3	$84.75	6.271%	$90.0647	$90.06	$90.05	$90.10
Purchase #4	$15.25	4.349%	$15.9132	$15.91	$15.90	$15.90
Purchase #5	$228.32	6.335%	$242.7841	$242.78	$242.80	$242.80
Purchase #6	$238.51	12.637%	$268.6505	$268.65	$268.65	$268.70
Purchase #7	$104.51	6.336%	$111.1318	$111.13	$111.15	$111.10
7 purchase totals =	$1,119.11		$1,212.2817	$1,212.27	$1,212.25	$1,212.40