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	$46.82	3.784%	$48.5917	$48.59	$48.60	$48.60
Purchase #2	$83.43	9.498%	$91.3542	$91.35	$91.35	$91.40
Purchase #3	$148.95	12.310%	$167.2857	$167.29	$167.30	$167.30
Purchase #4	$81.43	10.114%	$89.6658	$89.67	$89.65	$89.70
Purchase #5	$112.64	11.740%	$125.8639	$125.86	$125.85	$125.90
Purchase #6	$57.35	9.207%	$62.6302	$62.63	$62.65	$62.60
Purchase #7	$5.70	10.194%	$6.2811	$6.28	$6.30	$6.30
7 purchase totals =	$536.32		$591.6726	$591.67	$591.70	$591.80