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	$161.76	3.822%	$167.9425	$167.94	$167.95	$167.90
Purchase #2	$91.27	11.813%	$102.0517	$102.05	$102.05	$102.10
Purchase #3	$222.98	9.186%	$243.4629	$243.46	$243.45	$243.50
Purchase #4	$199.73	10.707%	$221.1151	$221.12	$221.10	$221.10
Purchase #5	$41.44	11.784%	$46.3233	$46.32	$46.30	$46.30
Purchase #6	$161.29	12.287%	$181.1077	$181.11	$181.10	$181.10
Purchase #7	$42.98	5.870%	$45.5029	$45.50	$45.50	$45.50
7 purchase totals =	$921.45		$1,007.5061	$1,007.50	$1,007.45	$1,007.50