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	$203.35	5.511%	$214.5566	$214.56	$214.55	$214.60
Purchase #2	$105.95	4.867%	$111.1066	$111.11	$111.10	$111.10
Purchase #3	$172.88	7.545%	$185.9238	$185.92	$185.90	$185.90
Purchase #4	$171.76	7.117%	$183.9842	$183.98	$184.00	$184.00
Purchase #5	$58.72	10.265%	$64.7476	$64.75	$64.75	$64.70
Purchase #6	$242.96	12.621%	$273.624	$273.62	$273.60	$273.60
Purchase #7	$145.68	7.697%	$156.893	$156.89	$156.90	$156.90
7 purchase totals =	$1,101.30		$1,190.8358	$1,190.83	$1,190.80	$1,190.80