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	$24.81	4.330%	$25.8843	$25.88	$25.90	$25.90
Purchase #2	$19.66	3.318%	$20.3123	$20.31	$20.30	$20.30
Purchase #3	$170.79	8.455%	$185.2303	$185.23	$185.25	$185.20
Purchase #4	$128.28	9.441%	$140.3909	$140.39	$140.40	$140.40
Purchase #5	$213.42	12.330%	$239.7347	$239.73	$239.75	$239.70
Purchase #6	$213.76	3.538%	$221.3228	$221.32	$221.30	$221.30
Purchase #7	$204.97	11.712%	$228.9761	$228.98	$229.00	$229.00
7 purchase totals =	$975.69		$1,061.8514	$1,061.84	$1,061.90	$1,061.80