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	$37.40	10.817%	$41.4456	$41.45	$41.45	$41.40
Purchase #2	$56.31	5.816%	$59.585	$59.59	$59.60	$59.60
Purchase #3	$100.73	6.284%	$107.0599	$107.06	$107.05	$107.10
Purchase #4	$173.75	5.442%	$183.2055	$183.21	$183.20	$183.20
Purchase #5	$42.40	7.627%	$45.6338	$45.63	$45.65	$45.60
Purchase #6	$50.92	10.423%	$56.2274	$56.23	$56.25	$56.20
Purchase #7	$162.84	13.237%	$184.3951	$184.40	$184.40	$184.40
7 purchase totals =	$624.35		$677.5523	$677.57	$677.60	$677.50