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	$148.69	5.144%	$156.3386	$156.34	$156.35	$156.30
Purchase #2	$62.67	8.292%	$67.8666	$67.87	$67.85	$67.90
Purchase #3	$223.74	11.261%	$248.9354	$248.94	$248.95	$248.90
Purchase #4	$27.54	3.695%	$28.5576	$28.56	$28.55	$28.60
Purchase #5	$139.76	3.657%	$144.871	$144.87	$144.85	$144.90
Purchase #6	$189.90	10.713%	$210.244	$210.24	$210.25	$210.20
Purchase #7	$211.42	7.224%	$226.693	$226.69	$226.70	$226.70
7 purchase totals =	$1,003.72		$1,083.5062	$1,083.51	$1,083.50	$1,083.50