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	$161.91	3.444%	$167.4862	$167.49	$167.50	$167.50
Purchase #2	$62.71	12.722%	$70.688	$70.69	$70.70	$70.70
Purchase #3	$69.56	4.266%	$72.5274	$72.53	$72.55	$72.50
Purchase #4	$223.37	9.609%	$244.8336	$244.83	$244.85	$244.80
Purchase #5	$178.97	3.179%	$184.6595	$184.66	$184.65	$184.70
Purchase #6	$115.95	12.256%	$130.1608	$130.16	$130.15	$130.20
Purchase #7	$125.27	13.261%	$141.8821	$141.88	$141.90	$141.90
7 purchase totals =	$937.74		$1,012.2376	$1,012.24	$1,012.30	$1,012.30