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	$110.82	13.654%	$125.9514	$125.95	$125.95	$126.00
Purchase #2	$219.38	8.845%	$238.7842	$238.78	$238.80	$238.80
Purchase #3	$166.71	4.448%	$174.1253	$174.13	$174.15	$174.10
Purchase #4	$179.96	8.743%	$195.6939	$195.69	$195.70	$195.70
Purchase #5	$89.29	3.836%	$92.7152	$92.72	$92.70	$92.70
Purchase #6	$235.41	6.532%	$250.787	$250.79	$250.80	$250.80
Purchase #7	$57.32	3.713%	$59.4483	$59.45	$59.45	$59.40
7 purchase totals =	$1,058.89		$1,137.5053	$1,137.51	$1,137.55	$1,137.50