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	$235.98	5.705%	$249.4427	$249.44	$249.45	$249.40
Purchase #2	$33.29	13.336%	$37.7296	$37.73	$37.75	$37.70
Purchase #3	$155.74	8.333%	$168.7178	$168.72	$168.70	$168.70
Purchase #4	$162.31	5.283%	$170.8848	$170.88	$170.90	$170.90
Purchase #5	$186.52	7.621%	$200.7347	$200.73	$200.75	$200.70
Purchase #6	$170.35	9.829%	$187.0937	$187.09	$187.10	$187.10
Purchase #7	$57.41	9.578%	$62.9087	$62.91	$62.90	$62.90
7 purchase totals =	$1,001.60		$1,077.5120	$1,077.50	$1,077.55	$1,077.40