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	$184.89	6.765%	$197.3978	$197.40	$197.40	$197.40
Purchase #2	$233.46	13.248%	$264.3888	$264.39	$264.40	$264.40
Purchase #3	$88.45	5.751%	$93.5368	$93.54	$93.55	$93.50
Purchase #4	$112.91	12.724%	$127.2767	$127.28	$127.30	$127.30
Purchase #5	$67.33	7.793%	$72.577	$72.58	$72.60	$72.60
Purchase #6	$234.81	4.341%	$245.0031	$245.00	$245.00	$245.00
Purchase #7	$65.63	7.192%	$70.3501	$70.35	$70.35	$70.40
7 purchase totals =	$987.48		$1,070.5303	$1,070.54	$1,070.60	$1,070.60