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	$197.59	11.652%	$220.6132	$220.61	$220.60	$220.60
Purchase #2	$25.92	10.557%	$28.6564	$28.66	$28.65	$28.70
Purchase #3	$130.34	8.788%	$141.7943	$141.79	$141.80	$141.80
Purchase #4	$179.43	3.585%	$185.8626	$185.86	$185.85	$185.90
Purchase #5	$221.31	8.590%	$240.3205	$240.32	$240.30	$240.30
Purchase #6	$146.91	6.227%	$156.0581	$156.06	$156.05	$156.10
Purchase #7	$55.49	7.360%	$59.5741	$59.57	$59.55	$59.60
7 purchase totals =	$956.99		$1,032.8792	$1,032.87	$1,032.80	$1,033.00