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	$142.35	7.461%	$152.9707	$152.97	$152.95	$153.00
Purchase #2	$228.28	6.629%	$243.4127	$243.41	$243.40	$243.40
Purchase #3	$179.84	5.552%	$189.8247	$189.82	$189.80	$189.80
Purchase #4	$162.78	3.418%	$168.3438	$168.34	$168.35	$168.30
Purchase #5	$28.96	13.290%	$32.8088	$32.81	$32.80	$32.80
Purchase #6	$136.38	6.175%	$144.8015	$144.80	$144.80	$144.80
Purchase #7	$92.60	6.318%	$98.4505	$98.45	$98.45	$98.50
7 purchase totals =	$971.19		$1,030.6127	$1,030.60	$1,030.55	$1,030.60