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	$174.76	4.666%	$182.9143	$182.91	$182.90	$182.90
Purchase #2	$169.79	13.608%	$192.895	$192.90	$192.90	$192.90
Purchase #3	$182.32	9.849%	$200.2767	$200.28	$200.30	$200.30
Purchase #4	$158.91	5.808%	$168.1395	$168.14	$168.15	$168.10
Purchase #5	$93.43	11.831%	$104.4837	$104.48	$104.50	$104.50
Purchase #6	$57.44	6.637%	$61.2523	$61.25	$61.25	$61.30
Purchase #7	$127.56	5.392%	$134.438	$134.44	$134.45	$134.40
7 purchase totals =	$964.21		$1,044.3995	$1,044.40	$1,044.45	$1,044.40