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	$193.86	13.735%	$220.4867	$220.49	$220.50	$220.50
Purchase #2	$191.64	12.223%	$215.0642	$215.06	$215.05	$215.10
Purchase #3	$181.54	4.790%	$190.2358	$190.24	$190.25	$190.20
Purchase #4	$155.34	11.673%	$173.4728	$173.47	$173.45	$173.50
Purchase #5	$65.52	9.376%	$71.6632	$71.66	$71.65	$71.70
Purchase #6	$53.92	12.336%	$60.5716	$60.57	$60.55	$60.60
Purchase #7	$84.51	4.791%	$88.5589	$88.56	$88.55	$88.60
7 purchase totals =	$926.33		$1,020.0532	$1,020.05	$1,020.00	$1,020.20