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	$87.37	7.350%	$93.7917	$93.79	$93.80	$93.80
Purchase #2	$190.68	10.189%	$210.1084	$210.11	$210.10	$210.10
Purchase #3	$203.63	4.402%	$212.5938	$212.59	$212.60	$212.60
Purchase #4	$47.35	10.412%	$52.2801	$52.28	$52.30	$52.30
Purchase #5	$115.36	7.414%	$123.9128	$123.91	$123.90	$123.90
Purchase #6	$167.40	10.610%	$185.1611	$185.16	$185.15	$185.20
Purchase #7	$196.47	13.412%	$222.8206	$222.82	$222.80	$222.80
7 purchase totals =	$1,008.26		$1,100.6685	$1,100.66	$1,100.65	$1,100.70