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	$12.73	12.847%	$14.3654	$14.37	$14.35	$14.40
Purchase #2	$18.75	12.772%	$21.1448	$21.14	$21.15	$21.10
Purchase #3	$116.59	9.405%	$127.5553	$127.56	$127.55	$127.60
Purchase #4	$115.43	11.523%	$128.731	$128.73	$128.75	$128.70
Purchase #5	$225.61	10.821%	$250.0233	$250.02	$250.00	$250.00
Purchase #6	$210.29	6.200%	$223.328	$223.33	$223.35	$223.30
Purchase #7	$166.34	8.814%	$181.0012	$181.00	$181.00	$181.00
7 purchase totals =	$865.74		$946.1490	$946.15	$946.15	$946.10