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	$235.50	10.718%	$260.7409	$260.74	$260.75	$260.70
Purchase #2	$41.44	10.415%	$45.756	$45.76	$45.75	$45.80
Purchase #3	$186.98	13.333%	$211.91	$211.91	$211.90	$211.90
Purchase #4	$108.39	10.764%	$120.0571	$120.06	$120.05	$120.10
Purchase #5	$94.26	11.692%	$105.2809	$105.28	$105.30	$105.30
Purchase #6	$119.49	9.807%	$131.2084	$131.21	$131.20	$131.20
Purchase #7	$171.62	8.726%	$186.5956	$186.60	$186.60	$186.60
7 purchase totals =	$957.68		$1,061.5489	$1,061.56	$1,061.55	$1,061.60