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	$220.31	9.489%	$241.2152	$241.22	$241.20	$241.20
Purchase #2	$79.73	12.181%	$89.4419	$89.44	$89.45	$89.40
Purchase #3	$77.42	12.192%	$86.859	$86.86	$86.85	$86.90
Purchase #4	$132.33	6.278%	$140.6377	$140.64	$140.65	$140.60
Purchase #5	$162.32	3.513%	$168.0223	$168.02	$168.00	$168.00
Purchase #6	$49.27	9.393%	$53.8979	$53.90	$53.90	$53.90
Purchase #7	$7.29	6.288%	$7.7484	$7.75	$7.75	$7.70
7 purchase totals =	$728.67		$787.8224	$787.83	$787.80	$787.70