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	$156.66	7.498%	$168.4064	$168.41	$168.40	$168.40
Purchase #2	$45.89	9.500%	$50.2496	$50.25	$50.25	$50.20
Purchase #3	$59.63	6.222%	$63.3402	$63.34	$63.35	$63.30
Purchase #4	$82.83	11.765%	$92.5749	$92.57	$92.55	$92.60
Purchase #5	$187.30	4.122%	$195.0205	$195.02	$195.00	$195.00
Purchase #6	$165.56	4.179%	$172.4788	$172.48	$172.50	$172.50
Purchase #7	$189.56	7.251%	$203.305	$203.31	$203.30	$203.30
7 purchase totals =	$887.43		$945.3754	$945.38	$945.35	$945.30