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	$238.60	12.872%	$269.3126	$269.31	$269.30	$269.30
Purchase #2	$58.98	4.741%	$61.7762	$61.78	$61.80	$61.80
Purchase #3	$158.48	4.104%	$164.984	$164.98	$165.00	$165.00
Purchase #4	$55.44	12.428%	$62.3301	$62.33	$62.35	$62.30
Purchase #5	$93.82	4.379%	$97.9284	$97.93	$97.95	$97.90
Purchase #6	$83.91	7.118%	$89.8827	$89.88	$89.90	$89.90
Purchase #7	$163.81	10.520%	$181.0428	$181.04	$181.05	$181.00
7 purchase totals =	$853.04		$927.2568	$927.25	$927.35	$927.20