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	$50.30	5.344%	$52.988	$52.99	$53.00	$53.00
Purchase #2	$108.83	13.850%	$123.903	$123.90	$123.90	$123.90
Purchase #3	$224.72	10.685%	$248.7313	$248.73	$248.75	$248.70
Purchase #4	$89.55	12.386%	$100.6417	$100.64	$100.65	$100.60
Purchase #5	$233.38	7.238%	$250.272	$250.27	$250.25	$250.30
Purchase #6	$79.67	8.544%	$86.477	$86.48	$86.50	$86.50
Purchase #7	$209.35	11.162%	$232.7176	$232.72	$232.70	$232.70
7 purchase totals =	$995.80		$1,095.7306	$1,095.73	$1,095.75	$1,095.70