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	$81.70	13.523%	$92.7483	$92.75	$92.75	$92.70
Purchase #2	$89.69	9.426%	$98.1442	$98.14	$98.15	$98.10
Purchase #3	$122.25	4.169%	$127.3466	$127.35	$127.35	$127.30
Purchase #4	$76.94	4.272%	$80.2269	$80.23	$80.25	$80.20
Purchase #5	$164.58	3.575%	$170.4637	$170.46	$170.45	$170.50
Purchase #6	$107.72	7.525%	$115.8259	$115.83	$115.85	$115.80
Purchase #7	$79.59	11.517%	$88.7564	$88.76	$88.75	$88.80
7 purchase totals =	$722.47		$773.5120	$773.52	$773.55	$773.40