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	$93.72	11.464%	$104.4641	$104.46	$104.45	$104.50
Purchase #2	$206.80	7.416%	$222.1363	$222.14	$222.15	$222.10
Purchase #3	$229.59	12.164%	$257.5173	$257.52	$257.50	$257.50
Purchase #4	$62.78	7.152%	$67.27	$67.27	$67.25	$67.30
Purchase #5	$17.79	4.681%	$18.6227	$18.62	$18.60	$18.60
Purchase #6	$47.36	12.769%	$53.4074	$53.41	$53.40	$53.40
Purchase #7	$222.52	4.865%	$233.3456	$233.35	$233.35	$233.30
7 purchase totals =	$880.56		$956.7634	$956.77	$956.70	$956.70