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	$185.95	12.336%	$208.8888	$208.89	$208.90	$208.90
Purchase #2	$176.25	7.111%	$188.7831	$188.78	$188.80	$188.80
Purchase #3	$222.54	11.572%	$248.2923	$248.29	$248.30	$248.30
Purchase #4	$168.82	11.547%	$188.3136	$188.31	$188.30	$188.30
Purchase #5	$85.77	6.133%	$91.0303	$91.03	$91.05	$91.00
Purchase #6	$59.78	8.538%	$64.884	$64.88	$64.90	$64.90
Purchase #7	$159.83	10.459%	$176.5466	$176.55	$176.55	$176.50
7 purchase totals =	$1,058.94		$1,166.7387	$1,166.73	$1,166.80	$1,166.70