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	$187.26	5.140%	$196.8852	$196.89	$196.90	$196.90
Purchase #2	$45.36	3.197%	$46.8102	$46.81	$46.80	$46.80
Purchase #3	$50.73	11.441%	$56.534	$56.53	$56.55	$56.50
Purchase #4	$115.40	10.236%	$127.2123	$127.21	$127.20	$127.20
Purchase #5	$219.67	3.574%	$227.521	$227.52	$227.50	$227.50
Purchase #6	$182.29	11.210%	$202.7247	$202.72	$202.70	$202.70
Purchase #7	$148.59	9.466%	$162.6555	$162.66	$162.65	$162.70
7 purchase totals =	$949.30		$1,020.3429	$1,020.34	$1,020.30	$1,020.30