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	$219.48	9.258%	$239.7995	$239.80	$239.80	$239.80
Purchase #2	$165.29	4.123%	$172.1049	$172.10	$172.10	$172.10
Purchase #3	$219.33	7.482%	$235.7403	$235.74	$235.75	$235.70
Purchase #4	$109.71	13.858%	$124.9136	$124.91	$124.90	$124.90
Purchase #5	$69.33	11.562%	$77.3459	$77.35	$77.35	$77.30
Purchase #6	$74.48	11.218%	$82.8352	$82.84	$82.85	$82.80
Purchase #7	$90.77	9.557%	$99.4449	$99.44	$99.45	$99.40
7 purchase totals =	$948.39		$1,032.1843	$1,032.18	$1,032.20	$1,032.00