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	$184.40	10.318%	$203.4264	$203.43	$203.45	$203.40
Purchase #2	$172.72	13.346%	$195.7712	$195.77	$195.75	$195.80
Purchase #3	$128.63	13.222%	$145.6375	$145.64	$145.65	$145.60
Purchase #4	$141.55	10.606%	$156.5628	$156.56	$156.55	$156.60
Purchase #5	$117.61	11.529%	$131.1693	$131.17	$131.15	$131.20
Purchase #6	$196.53	9.794%	$215.7781	$215.78	$215.80	$215.80
Purchase #7	$21.89	4.400%	$22.8532	$22.85	$22.85	$22.90
7 purchase totals =	$963.33		$1,071.1985	$1,071.20	$1,071.20	$1,071.30