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	$83.61	10.244%	$92.175	$92.18	$92.20	$92.20
Purchase #2	$53.66	9.737%	$58.8849	$58.88	$58.90	$58.90
Purchase #3	$31.82	11.347%	$35.4306	$35.43	$35.45	$35.40
Purchase #4	$28.73	11.121%	$31.9251	$31.93	$31.95	$31.90
Purchase #5	$52.32	4.698%	$54.778	$54.78	$54.80	$54.80
Purchase #6	$67.37	4.427%	$70.3525	$70.35	$70.35	$70.40
Purchase #7	$135.45	7.414%	$145.4923	$145.49	$145.50	$145.50
7 purchase totals =	$452.96		$489.0384	$489.04	$489.15	$489.10