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	$79.75	11.133%	$88.6286	$88.63	$88.65	$88.60
Purchase #2	$159.40	5.222%	$167.7239	$167.72	$167.70	$167.70
Purchase #3	$175.59	11.514%	$195.8074	$195.81	$195.80	$195.80
Purchase #4	$76.41	7.691%	$82.2867	$82.29	$82.30	$82.30
Purchase #5	$233.39	4.632%	$244.2006	$244.20	$244.20	$244.20
Purchase #6	$69.86	5.485%	$73.6918	$73.69	$73.70	$73.70
Purchase #7	$146.90	12.647%	$165.4784	$165.48	$165.50	$165.50
7 purchase totals =	$941.30		$1,017.8174	$1,017.82	$1,017.85	$1,017.80