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	$174.89	8.292%	$189.3919	$189.39	$189.40	$189.40
Purchase #2	$72.52	8.302%	$78.5406	$78.54	$78.55	$78.50
Purchase #3	$186.43	12.303%	$209.3665	$209.37	$209.35	$209.40
Purchase #4	$119.79	11.861%	$133.9983	$134.00	$134.00	$134.00
Purchase #5	$190.33	5.486%	$200.7715	$200.77	$200.75	$200.80
Purchase #6	$235.29	12.497%	$264.6942	$264.69	$264.70	$264.70
Purchase #7	$65.84	3.546%	$68.1747	$68.17	$68.15	$68.20
7 purchase totals =	$1,045.09		$1,144.9377	$1,144.93	$1,144.90	$1,145.00