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	$67.79	7.117%	$72.6146	$72.61	$72.60	$72.60
Purchase #2	$117.68	11.375%	$131.0661	$131.07	$131.05	$131.10
Purchase #3	$159.82	12.656%	$180.0468	$180.05	$180.05	$180.00
Purchase #4	$175.61	3.301%	$181.4069	$181.41	$181.40	$181.40
Purchase #5	$159.98	5.781%	$169.2284	$169.23	$169.25	$169.20
Purchase #6	$98.33	6.585%	$104.805	$104.81	$104.80	$104.80
Purchase #7	$203.49	9.672%	$223.1716	$223.17	$223.15	$223.20
7 purchase totals =	$982.70		$1,062.3394	$1,062.35	$1,062.30	$1,062.30