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	$112.95	12.717%	$127.3139	$127.31	$127.30	$127.30
Purchase #2	$86.40	5.791%	$91.4034	$91.40	$91.40	$91.40
Purchase #3	$250.92	5.170%	$263.8926	$263.89	$263.90	$263.90
Purchase #4	$215.56	13.741%	$245.1801	$245.18	$245.20	$245.20
Purchase #5	$85.43	13.613%	$97.0596	$97.06	$97.05	$97.10
Purchase #6	$154.55	10.526%	$170.8179	$170.82	$170.80	$170.80
Purchase #7	$36.97	6.181%	$39.2551	$39.26	$39.25	$39.30
7 purchase totals =	$942.78		$1,034.9226	$1,034.92	$1,034.90	$1,035.00