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	$203.42	3.411%	$210.3587	$210.36	$210.35	$210.40
Purchase #2	$151.85	5.289%	$159.8813	$159.88	$159.90	$159.90
Purchase #3	$243.35	5.138%	$255.8533	$255.85	$255.85	$255.90
Purchase #4	$10.64	10.483%	$11.7554	$11.76	$11.75	$11.80
Purchase #5	$82.62	3.496%	$85.5084	$85.51	$85.50	$85.50
Purchase #6	$131.51	10.814%	$145.7315	$145.73	$145.75	$145.70
Purchase #7	$68.70	7.404%	$73.7865	$73.79	$73.80	$73.80
7 purchase totals =	$892.09		$942.8751	$942.88	$942.90	$943.00