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	$162.50	3.525%	$168.2281	$168.23	$168.25	$168.20
Purchase #2	$220.37	13.569%	$250.272	$250.27	$250.25	$250.30
Purchase #3	$187.75	3.496%	$194.3137	$194.31	$194.30	$194.30
Purchase #4	$104.56	13.251%	$118.4152	$118.42	$118.40	$118.40
Purchase #5	$147.89	7.774%	$159.387	$159.39	$159.40	$159.40
Purchase #6	$220.91	10.578%	$244.2779	$244.28	$244.30	$244.30
Purchase #7	$29.74	9.844%	$32.6676	$32.67	$32.65	$32.70
7 purchase totals =	$1,073.72		$1,167.5615	$1,167.57	$1,167.55	$1,167.60