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	$174.52	9.844%	$191.6997	$191.70	$191.70	$191.70
Purchase #2	$235.91	11.130%	$262.1668	$262.17	$262.15	$262.20
Purchase #3	$184.87	7.579%	$198.8813	$198.88	$198.90	$198.90
Purchase #4	$69.41	7.478%	$74.6005	$74.60	$74.60	$74.60
Purchase #5	$195.86	7.109%	$209.7837	$209.78	$209.80	$209.80
Purchase #6	$52.41	13.109%	$59.2804	$59.28	$59.30	$59.30
Purchase #7	$162.79	7.419%	$174.8674	$174.87	$174.85	$174.90
7 purchase totals =	$1,075.77		$1,171.2798	$1,171.28	$1,171.30	$1,171.40