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	$31.27	12.667%	$35.231	$35.23	$35.25	$35.20
Purchase #2	$119.87	7.334%	$128.6613	$128.66	$128.65	$128.70
Purchase #3	$160.37	7.353%	$172.162	$172.16	$172.15	$172.20
Purchase #4	$38.66	7.624%	$41.6074	$41.61	$41.60	$41.60
Purchase #5	$190.62	4.133%	$198.4983	$198.50	$198.50	$198.50
Purchase #6	$113.76	12.415%	$127.8833	$127.88	$127.90	$127.90
Purchase #7	$138.29	10.738%	$153.1396	$153.14	$153.15	$153.10
7 purchase totals =	$792.84		$857.1829	$857.18	$857.20	$857.20