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	$94.92	8.541%	$103.0271	$103.03	$103.05	$103.00
Purchase #2	$208.44	6.653%	$222.3075	$222.31	$222.30	$222.30
Purchase #3	$230.29	7.360%	$247.2393	$247.24	$247.25	$247.20
Purchase #4	$43.54	7.756%	$46.917	$46.92	$46.90	$46.90
Purchase #5	$29.55	8.692%	$32.1185	$32.12	$32.10	$32.10
Purchase #6	$216.89	5.253%	$228.2832	$228.28	$228.30	$228.30
Purchase #7	$164.76	4.331%	$171.8958	$171.90	$171.90	$171.90
7 purchase totals =	$988.39		$1,051.7884	$1,051.80	$1,051.80	$1,051.70