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	$211.56	10.330%	$233.4141	$233.41	$233.40	$233.40
Purchase #2	$172.78	8.610%	$187.6564	$187.66	$187.65	$187.70
Purchase #3	$88.29	4.213%	$92.0097	$92.01	$92.00	$92.00
Purchase #4	$85.46	3.263%	$88.2486	$88.25	$88.25	$88.20
Purchase #5	$121.71	6.720%	$129.8889	$129.89	$129.90	$129.90
Purchase #6	$243.36	13.173%	$275.4178	$275.42	$275.40	$275.40
Purchase #7	$75.32	13.156%	$85.2291	$85.23	$85.25	$85.20
7 purchase totals =	$998.48		$1,091.8646	$1,091.87	$1,091.85	$1,091.80