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	$136.75	12.473%	$153.8068	$153.81	$153.80	$153.80
Purchase #2	$134.92	9.294%	$147.4595	$147.46	$147.45	$147.50
Purchase #3	$128.32	5.575%	$135.4738	$135.47	$135.45	$135.50
Purchase #4	$86.47	11.814%	$96.6856	$96.69	$96.70	$96.70
Purchase #5	$168.39	4.215%	$175.4876	$175.49	$175.50	$175.50
Purchase #6	$123.60	5.512%	$130.4128	$130.41	$130.40	$130.40
Purchase #7	$42.82	6.362%	$45.5442	$45.54	$45.55	$45.50
7 purchase totals =	$821.27		$884.8703	$884.87	$884.85	$884.90