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	$158.65	13.627%	$180.2692	$180.27	$180.25	$180.30
Purchase #2	$188.85	13.549%	$214.4373	$214.44	$214.45	$214.40
Purchase #3	$64.67	11.150%	$71.8807	$71.88	$71.90	$71.90
Purchase #4	$31.32	12.822%	$35.3359	$35.34	$35.35	$35.30
Purchase #5	$241.32	3.349%	$249.4018	$249.40	$249.40	$249.40
Purchase #6	$216.31	12.543%	$243.4418	$243.44	$243.45	$243.40
Purchase #7	$163.28	13.470%	$185.2738	$185.27	$185.25	$185.30
7 purchase totals =	$1,064.40		$1,180.0405	$1,180.04	$1,180.05	$1,180.00