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	$49.43	10.758%	$54.7477	$54.75	$54.75	$54.70
Purchase #2	$106.79	12.246%	$119.8675	$119.87	$119.85	$119.90
Purchase #3	$166.80	11.156%	$185.4082	$185.41	$185.40	$185.40
Purchase #4	$42.36	6.507%	$45.1164	$45.12	$45.10	$45.10
Purchase #5	$213.46	7.155%	$228.7331	$228.73	$228.75	$228.70
Purchase #6	$240.49	12.739%	$271.126	$271.13	$271.15	$271.10
Purchase #7	$188.65	12.314%	$211.8804	$211.88	$211.90	$211.90
7 purchase totals =	$1,007.98		$1,116.8793	$1,116.89	$1,116.90	$1,116.80