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	$67.31	7.528%	$72.3771	$72.38	$72.40	$72.40
Purchase #2	$176.85	3.519%	$183.0734	$183.07	$183.05	$183.10
Purchase #3	$63.91	13.651%	$72.6344	$72.63	$72.65	$72.60
Purchase #4	$186.40	3.251%	$192.4599	$192.46	$192.45	$192.50
Purchase #5	$155.98	11.654%	$174.1579	$174.16	$174.15	$174.20
Purchase #6	$234.36	3.333%	$242.1712	$242.17	$242.15	$242.20
Purchase #7	$226.65	9.357%	$247.8576	$247.86	$247.85	$247.90
7 purchase totals =	$1,111.46		$1,184.7315	$1,184.73	$1,184.70	$1,184.90