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	$32.73	9.745%	$35.9195	$35.92	$35.90	$35.90
Purchase #2	$248.87	7.339%	$267.1346	$267.13	$267.15	$267.10
Purchase #3	$55.89	6.741%	$59.6575	$59.66	$59.65	$59.70
Purchase #4	$238.72	8.624%	$259.3072	$259.31	$259.30	$259.30
Purchase #5	$85.59	13.209%	$96.8956	$96.90	$96.90	$96.90
Purchase #6	$110.69	8.304%	$119.8817	$119.88	$119.90	$119.90
Purchase #7	$221.76	6.439%	$236.0391	$236.04	$236.05	$236.00
7 purchase totals =	$994.25		$1,074.8352	$1,074.84	$1,074.85	$1,074.80