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	$93.32	6.554%	$99.4362	$99.44	$99.45	$99.40
Purchase #2	$25.64	6.383%	$27.2766	$27.28	$27.30	$27.30
Purchase #3	$28.55	9.125%	$31.1552	$31.16	$31.15	$31.20
Purchase #4	$110.87	13.400%	$125.7266	$125.73	$125.75	$125.70
Purchase #5	$142.82	9.570%	$156.4879	$156.49	$156.50	$156.50
Purchase #6	$87.56	5.428%	$92.3128	$92.31	$92.30	$92.30
Purchase #7	$179.39	11.683%	$200.3481	$200.35	$200.35	$200.30
7 purchase totals =	$668.15		$732.7434	$732.76	$732.80	$732.70