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	$52.58	12.772%	$59.2955	$59.30	$59.30	$59.30
Purchase #2	$224.42	6.163%	$238.251	$238.25	$238.25	$238.30
Purchase #3	$216.68	10.410%	$239.2364	$239.24	$239.25	$239.20
Purchase #4	$156.86	6.532%	$167.1061	$167.11	$167.10	$167.10
Purchase #5	$104.48	3.515%	$108.1525	$108.15	$108.15	$108.20
Purchase #6	$226.86	7.346%	$243.5251	$243.53	$243.55	$243.50
Purchase #7	$92.91	11.753%	$103.8297	$103.83	$103.85	$103.80
7 purchase totals =	$1,074.79		$1,159.3963	$1,159.41	$1,159.45	$1,159.40