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	$56.33	4.104%	$58.6418	$58.64	$58.65	$58.60
Purchase #2	$75.30	3.669%	$78.0628	$78.06	$78.05	$78.10
Purchase #3	$82.68	5.607%	$87.3159	$87.32	$87.30	$87.30
Purchase #4	$200.28	4.631%	$209.555	$209.56	$209.55	$209.60
Purchase #5	$52.88	5.270%	$55.6668	$55.67	$55.65	$55.70
Purchase #6	$47.88	13.119%	$54.1614	$54.16	$54.15	$54.20
Purchase #7	$68.37	5.747%	$72.2992	$72.30	$72.30	$72.30
7 purchase totals =	$583.72		$615.7029	$615.71	$615.65	$615.80