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	$211.72	13.316%	$239.9126	$239.91	$239.90	$239.90
Purchase #2	$55.36	12.488%	$62.2734	$62.27	$62.25	$62.30
Purchase #3	$250.43	5.279%	$263.6502	$263.65	$263.65	$263.70
Purchase #4	$48.46	3.862%	$50.3315	$50.33	$50.35	$50.30
Purchase #5	$218.97	13.287%	$248.0645	$248.06	$248.05	$248.10
Purchase #6	$166.83	3.445%	$172.5773	$172.58	$172.60	$172.60
Purchase #7	$104.54	6.782%	$111.6299	$111.63	$111.65	$111.60
7 purchase totals =	$1,056.31		$1,148.4394	$1,148.43	$1,148.45	$1,148.50