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	$191.73	8.496%	$208.0194	$208.02	$208.00	$208.00
Purchase #2	$196.40	5.253%	$206.7169	$206.72	$206.70	$206.70
Purchase #3	$243.71	8.275%	$263.877	$263.88	$263.90	$263.90
Purchase #4	$77.95	8.688%	$84.7223	$84.72	$84.70	$84.70
Purchase #5	$107.82	3.359%	$111.4417	$111.44	$111.45	$111.40
Purchase #6	$19.57	5.293%	$20.6058	$20.61	$20.60	$20.60
Purchase #7	$228.54	9.711%	$250.7335	$250.73	$250.75	$250.70
7 purchase totals =	$1,065.72		$1,146.1166	$1,146.12	$1,146.10	$1,146.00