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	$52.61	11.633%	$58.7301	$58.73	$58.75	$58.70
Purchase #2	$56.56	13.199%	$64.0254	$64.03	$64.05	$64.00
Purchase #3	$71.25	10.178%	$78.5018	$78.50	$78.50	$78.50
Purchase #4	$94.26	6.135%	$100.0429	$100.04	$100.05	$100.00
Purchase #5	$148.34	12.481%	$166.8543	$166.85	$166.85	$166.90
Purchase #6	$128.28	10.780%	$142.1086	$142.11	$142.10	$142.10
Purchase #7	$69.29	5.356%	$73.0012	$73.00	$73.00	$73.00
7 purchase totals =	$620.59		$683.2643	$683.26	$683.30	$683.20