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	$223.61	11.700%	$249.7724	$249.77	$249.75	$249.80
Purchase #2	$51.98	6.304%	$55.2568	$55.26	$55.25	$55.30
Purchase #3	$215.41	13.113%	$243.6567	$243.66	$243.65	$243.70
Purchase #4	$241.98	3.428%	$250.2751	$250.28	$250.30	$250.30
Purchase #5	$211.90	7.465%	$227.7183	$227.72	$227.70	$227.70
Purchase #6	$179.88	4.732%	$188.3919	$188.39	$188.40	$188.40
Purchase #7	$229.61	10.540%	$253.8109	$253.81	$253.80	$253.80
7 purchase totals =	$1,354.37		$1,468.8821	$1,468.89	$1,468.85	$1,469.00