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	$148.30	5.525%	$156.4936	$156.49	$156.50	$156.50
Purchase #2	$159.98	7.725%	$172.3385	$172.34	$172.35	$172.30
Purchase #3	$183.67	11.488%	$204.77	$204.77	$204.75	$204.80
Purchase #4	$63.64	11.842%	$71.1762	$71.18	$71.20	$71.20
Purchase #5	$236.73	11.470%	$263.8829	$263.88	$263.90	$263.90
Purchase #6	$78.45	13.802%	$89.2777	$89.28	$89.30	$89.30
Purchase #7	$195.69	7.317%	$210.0086	$210.01	$210.00	$210.00
7 purchase totals =	$1,066.46		$1,167.9475	$1,167.95	$1,168.00	$1,168.00