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	$239.34	3.573%	$247.8916	$247.89	$247.90	$247.90
Purchase #2	$47.30	5.422%	$49.8646	$49.86	$49.85	$49.90
Purchase #3	$152.61	6.404%	$162.3831	$162.38	$162.40	$162.40
Purchase #4	$142.27	9.481%	$155.7586	$155.76	$155.75	$155.80
Purchase #5	$171.72	11.807%	$191.995	$192.00	$192.00	$192.00
Purchase #6	$222.80	5.525%	$235.1097	$235.11	$235.10	$235.10
Purchase #7	$31.85	3.824%	$33.0679	$33.07	$33.05	$33.10
7 purchase totals =	$1,007.89		$1,076.0705	$1,076.07	$1,076.05	$1,076.20