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	$92.37	5.487%	$97.4383	$97.44	$97.45	$97.40
Purchase #2	$101.40	4.478%	$105.9407	$105.94	$105.95	$105.90
Purchase #3	$213.32	4.594%	$223.1199	$223.12	$223.10	$223.10
Purchase #4	$246.44	8.773%	$268.0602	$268.06	$268.05	$268.10
Purchase #5	$82.45	11.298%	$91.7652	$91.77	$91.75	$91.80
Purchase #6	$39.43	7.680%	$42.4582	$42.46	$42.45	$42.50
Purchase #7	$69.46	3.642%	$71.9897	$71.99	$72.00	$72.00
7 purchase totals =	$844.87		$900.7722	$900.78	$900.75	$900.80