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	$218.68	3.337%	$225.9774	$225.98	$226.00	$226.00
Purchase #2	$19.36	13.317%	$21.9382	$21.94	$21.95	$21.90
Purchase #3	$204.33	12.244%	$229.3482	$229.35	$229.35	$229.30
Purchase #4	$168.27	3.498%	$174.1561	$174.16	$174.15	$174.20
Purchase #5	$188.27	4.238%	$196.2489	$196.25	$196.25	$196.20
Purchase #6	$11.47	7.170%	$12.2924	$12.29	$12.30	$12.30
Purchase #7	$127.39	12.221%	$142.9583	$142.96	$142.95	$143.00
7 purchase totals =	$937.77		$1,002.9195	$1,002.93	$1,002.95	$1,002.90