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	$101.92	7.852%	$109.9228	$109.92	$109.90	$109.90
Purchase #2	$71.27	6.515%	$75.9132	$75.91	$75.90	$75.90
Purchase #3	$168.35	6.769%	$179.7456	$179.75	$179.75	$179.70
Purchase #4	$204.94	5.582%	$216.3798	$216.38	$216.40	$216.40
Purchase #5	$51.83	3.655%	$53.7244	$53.72	$53.70	$53.70
Purchase #6	$104.63	6.548%	$111.4812	$111.48	$111.50	$111.50
Purchase #7	$242.73	13.708%	$276.0034	$276.00	$276.00	$276.00
7 purchase totals =	$945.67		$1,023.1704	$1,023.16	$1,023.15	$1,023.10