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	$48.69	3.539%	$50.4131	$50.41	$50.40	$50.40
Purchase #2	$202.53	6.253%	$215.1942	$215.19	$215.20	$215.20
Purchase #3	$64.50	12.239%	$72.3942	$72.39	$72.40	$72.40
Purchase #4	$225.66	8.566%	$244.99	$244.99	$245.00	$245.00
Purchase #5	$168.43	10.288%	$185.7581	$185.76	$185.75	$185.80
Purchase #6	$245.98	13.581%	$279.3865	$279.39	$279.40	$279.40
Purchase #7	$91.88	8.416%	$99.6126	$99.61	$99.60	$99.60
7 purchase totals =	$1,047.67		$1,147.7487	$1,147.74	$1,147.75	$1,147.80