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	$139.83	9.352%	$152.9069	$152.91	$152.90	$152.90
Purchase #2	$117.66	6.133%	$124.8761	$124.88	$124.90	$124.90
Purchase #3	$173.88	6.437%	$185.0727	$185.07	$185.05	$185.10
Purchase #4	$52.76	3.379%	$54.5428	$54.54	$54.55	$54.50
Purchase #5	$93.76	6.601%	$99.9491	$99.95	$99.95	$99.90
Purchase #6	$230.36	9.152%	$251.4425	$251.44	$251.45	$251.40
Purchase #7	$53.44	6.354%	$56.8356	$56.84	$56.85	$56.80
7 purchase totals =	$861.69		$925.6257	$925.63	$925.65	$925.50