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	$179.85	4.761%	$188.4127	$188.41	$188.40	$188.40
Purchase #2	$206.25	9.364%	$225.5633	$225.56	$225.55	$225.60
Purchase #3	$178.87	9.326%	$195.5514	$195.55	$195.55	$195.60
Purchase #4	$111.51	3.221%	$115.1017	$115.10	$115.10	$115.10
Purchase #5	$179.72	11.456%	$200.3087	$200.31	$200.30	$200.30
Purchase #6	$11.27	7.467%	$12.1115	$12.11	$12.10	$12.10
Purchase #7	$115.73	10.115%	$127.4361	$127.44	$127.45	$127.40
7 purchase totals =	$983.20		$1,064.4854	$1,064.48	$1,064.45	$1,064.50