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	$179.83	3.250%	$185.6745	$185.67	$185.65	$185.70
Purchase #2	$188.83	3.710%	$195.8356	$195.84	$195.85	$195.80
Purchase #3	$219.70	6.180%	$233.2775	$233.28	$233.30	$233.30
Purchase #4	$7.58	7.324%	$8.1352	$8.14	$8.15	$8.10
Purchase #5	$115.29	11.543%	$128.5979	$128.60	$128.60	$128.60
Purchase #6	$111.34	6.258%	$118.3077	$118.31	$118.30	$118.30
Purchase #7	$243.87	13.119%	$275.8633	$275.86	$275.85	$275.90
7 purchase totals =	$1,066.44		$1,145.6917	$1,145.70	$1,145.70	$1,145.70