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	$236.29	4.646%	$247.268	$247.27	$247.25	$247.30
Purchase #2	$247.89	6.342%	$263.6112	$263.61	$263.60	$263.60
Purchase #3	$159.28	12.853%	$179.7523	$179.75	$179.75	$179.80
Purchase #4	$68.52	12.567%	$77.1309	$77.13	$77.15	$77.10
Purchase #5	$50.88	8.728%	$55.3208	$55.32	$55.30	$55.30
Purchase #6	$177.59	6.196%	$188.5935	$188.59	$188.60	$188.60
Purchase #7	$62.29	3.439%	$64.4322	$64.43	$64.45	$64.40
7 purchase totals =	$1,002.74		$1,076.1089	$1,076.10	$1,076.10	$1,076.10