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	$153.64	5.636%	$162.2992	$162.30	$162.30	$162.30
Purchase #2	$35.56	6.593%	$37.9045	$37.90	$37.90	$37.90
Purchase #3	$244.90	5.840%	$259.2022	$259.20	$259.20	$259.20
Purchase #4	$218.41	12.279%	$245.2286	$245.23	$245.25	$245.20
Purchase #5	$71.86	11.370%	$80.0305	$80.03	$80.05	$80.00
Purchase #6	$225.87	12.254%	$253.5481	$253.55	$253.55	$253.50
Purchase #7	$244.70	11.265%	$272.2655	$272.27	$272.25	$272.30
7 purchase totals =	$1,194.94		$1,310.4786	$1,310.48	$1,310.50	$1,310.40