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	$175.31	3.245%	$180.9988	$181.00	$181.00	$181.00
Purchase #2	$175.82	11.484%	$196.0112	$196.01	$196.00	$196.00
Purchase #3	$89.57	11.816%	$100.1536	$100.15	$100.15	$100.20
Purchase #4	$51.87	12.407%	$58.3055	$58.31	$58.30	$58.30
Purchase #5	$178.97	9.288%	$195.5927	$195.59	$195.60	$195.60
Purchase #6	$231.56	5.171%	$243.534	$243.53	$243.55	$243.50
Purchase #7	$91.55	13.625%	$104.0237	$104.02	$104.00	$104.00
7 purchase totals =	$994.65		$1,078.6195	$1,078.61	$1,078.60	$1,078.60