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	$161.27	12.873%	$182.0303	$182.03	$182.05	$182.00
Purchase #2	$79.59	7.494%	$85.5545	$85.55	$85.55	$85.60
Purchase #3	$209.29	9.550%	$229.2772	$229.28	$229.30	$229.30
Purchase #4	$245.69	6.362%	$261.3208	$261.32	$261.30	$261.30
Purchase #5	$72.36	13.708%	$82.2791	$82.28	$82.30	$82.30
Purchase #6	$46.94	9.132%	$51.2266	$51.23	$51.25	$51.20
Purchase #7	$70.89	8.855%	$77.1673	$77.17	$77.15	$77.20
7 purchase totals =	$886.03		$968.8558	$968.86	$968.90	$968.90