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	$146.69	9.571%	$160.7297	$160.73	$160.75	$160.70
Purchase #2	$73.80	11.303%	$82.1416	$82.14	$82.15	$82.10
Purchase #3	$102.49	8.572%	$111.2754	$111.28	$111.30	$111.30
Purchase #4	$142.46	12.427%	$160.1635	$160.16	$160.15	$160.20
Purchase #5	$249.26	10.608%	$275.7015	$275.70	$275.70	$275.70
Purchase #6	$109.45	8.868%	$119.156	$119.16	$119.15	$119.20
Purchase #7	$171.88	6.769%	$183.5146	$183.51	$183.50	$183.50
7 purchase totals =	$996.03		$1,092.6823	$1,092.68	$1,092.70	$1,092.70