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	$185.92	4.417%	$194.1321	$194.13	$194.15	$194.10
Purchase #2	$209.78	11.289%	$233.4621	$233.46	$233.45	$233.50
Purchase #3	$205.97	8.357%	$223.1829	$223.18	$223.20	$223.20
Purchase #4	$47.75	13.791%	$54.3352	$54.34	$54.35	$54.30
Purchase #5	$5.57	11.860%	$6.2306	$6.23	$6.25	$6.20
Purchase #6	$102.87	6.554%	$109.6121	$109.61	$109.60	$109.60
Purchase #7	$160.63	13.465%	$182.2588	$182.26	$182.25	$182.30
7 purchase totals =	$918.49		$1,003.2138	$1,003.21	$1,003.25	$1,003.20