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	$198.76	12.377%	$223.3605	$223.36	$223.35	$223.40
Purchase #2	$180.56	13.789%	$205.4574	$205.46	$205.45	$205.50
Purchase #3	$176.50	5.454%	$186.1263	$186.13	$186.15	$186.10
Purchase #4	$158.39	4.512%	$165.5366	$165.54	$165.55	$165.50
Purchase #5	$179.27	5.260%	$188.6996	$188.70	$188.70	$188.70
Purchase #6	$31.28	11.187%	$34.7793	$34.78	$34.80	$34.80
Purchase #7	$98.96	4.737%	$103.6477	$103.65	$103.65	$103.60
7 purchase totals =	$1,023.72		$1,107.6074	$1,107.62	$1,107.65	$1,107.60