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	$152.93	13.393%	$173.4119	$173.41	$173.40	$173.40
Purchase #2	$178.34	4.259%	$185.9355	$185.94	$185.95	$185.90
Purchase #3	$215.48	10.827%	$238.81	$238.81	$238.80	$238.80
Purchase #4	$205.46	3.117%	$211.8642	$211.86	$211.85	$211.90
Purchase #5	$109.54	8.339%	$118.6745	$118.67	$118.65	$118.70
Purchase #6	$90.80	9.177%	$99.1327	$99.13	$99.15	$99.10
Purchase #7	$59.73	6.287%	$63.4852	$63.49	$63.50	$63.50
7 purchase totals =	$1,012.28		$1,091.3140	$1,091.31	$1,091.30	$1,091.30