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	$26.92	6.586%	$28.693	$28.69	$28.70	$28.70
Purchase #2	$43.37	13.344%	$49.1573	$49.16	$49.15	$49.20
Purchase #3	$229.98	10.547%	$254.236	$254.24	$254.25	$254.20
Purchase #4	$83.30	3.701%	$86.3829	$86.38	$86.40	$86.40
Purchase #5	$122.53	4.104%	$127.5586	$127.56	$127.55	$127.60
Purchase #6	$72.96	7.550%	$78.4685	$78.47	$78.45	$78.50
Purchase #7	$102.98	7.172%	$110.3657	$110.37	$110.35	$110.40
7 purchase totals =	$682.04		$734.8620	$734.87	$734.85	$735.00