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	$114.98	9.745%	$126.1848	$126.18	$126.20	$126.20
Purchase #2	$55.82	6.586%	$59.4963	$59.50	$59.50	$59.50
Purchase #3	$39.84	13.258%	$45.122	$45.12	$45.10	$45.10
Purchase #4	$247.44	12.474%	$278.3057	$278.31	$278.30	$278.30
Purchase #5	$29.75	11.759%	$33.2483	$33.25	$33.25	$33.20
Purchase #6	$82.71	6.395%	$87.9993	$88.00	$88.00	$88.00
Purchase #7	$127.28	12.153%	$142.7483	$142.75	$142.75	$142.70
7 purchase totals =	$697.82		$773.1047	$773.11	$773.10	$773.00