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	$167.56	7.155%	$179.5489	$179.55	$179.55	$179.50
Purchase #2	$63.49	10.761%	$70.3222	$70.32	$70.30	$70.30
Purchase #3	$165.63	5.532%	$174.7927	$174.79	$174.80	$174.80
Purchase #4	$107.31	7.648%	$115.5171	$115.52	$115.50	$115.50
Purchase #5	$208.90	6.604%	$222.6958	$222.70	$222.70	$222.70
Purchase #6	$192.79	10.698%	$213.4147	$213.41	$213.40	$213.40
Purchase #7	$32.33	4.396%	$33.7512	$33.75	$33.75	$33.80
7 purchase totals =	$938.01		$1,010.0426	$1,010.04	$1,010.00	$1,010.00