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	$58.39	11.201%	$64.9303	$64.93	$64.95	$64.90
Purchase #2	$86.39	3.568%	$89.4724	$89.47	$89.45	$89.50
Purchase #3	$124.45	13.624%	$141.4051	$141.41	$141.40	$141.40
Purchase #4	$112.74	13.142%	$127.5563	$127.56	$127.55	$127.60
Purchase #5	$160.80	12.218%	$180.4465	$180.45	$180.45	$180.40
Purchase #6	$159.77	5.326%	$168.2794	$168.28	$168.30	$168.30
Purchase #7	$247.70	13.109%	$280.171	$280.17	$280.15	$280.20
7 purchase totals =	$950.24		$1,052.2610	$1,052.27	$1,052.25	$1,052.30