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	$100.58	3.649%	$104.2502	$104.25	$104.25	$104.30
Purchase #2	$98.29	11.673%	$109.7634	$109.76	$109.75	$109.80
Purchase #3	$57.64	3.178%	$59.4718	$59.47	$59.45	$59.50
Purchase #4	$223.62	10.603%	$247.3304	$247.33	$247.35	$247.30
Purchase #5	$176.75	3.460%	$182.8656	$182.87	$182.85	$182.90
Purchase #6	$75.72	10.348%	$83.5555	$83.56	$83.55	$83.60
Purchase #7	$179.82	3.170%	$185.5203	$185.52	$185.50	$185.50
7 purchase totals =	$912.42		$972.7572	$972.76	$972.70	$972.90