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	$133.48	12.302%	$149.9007	$149.90	$149.90	$149.90
Purchase #2	$83.63	7.369%	$89.7927	$89.79	$89.80	$89.80
Purchase #3	$123.83	4.436%	$129.3231	$129.32	$129.30	$129.30
Purchase #4	$154.90	5.143%	$162.8665	$162.87	$162.85	$162.90
Purchase #5	$95.73	13.417%	$108.5741	$108.57	$108.55	$108.60
Purchase #6	$31.85	4.466%	$33.2724	$33.27	$33.25	$33.30
Purchase #7	$209.27	6.446%	$222.7595	$222.76	$222.75	$222.80
7 purchase totals =	$832.69		$896.4890	$896.48	$896.40	$896.60