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	$76.42	12.430%	$85.919	$85.92	$85.90	$85.90
Purchase #2	$73.37	6.490%	$78.1317	$78.13	$78.15	$78.10
Purchase #3	$177.82	7.413%	$191.0018	$191.00	$191.00	$191.00
Purchase #4	$245.26	9.793%	$269.2783	$269.28	$269.30	$269.30
Purchase #5	$245.90	10.160%	$270.8834	$270.88	$270.90	$270.90
Purchase #6	$68.71	11.135%	$76.3609	$76.36	$76.35	$76.40
Purchase #7	$45.98	8.262%	$49.7789	$49.78	$49.80	$49.80
7 purchase totals =	$933.46		$1,021.3540	$1,021.35	$1,021.40	$1,021.40