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	$236.56	5.814%	$250.3136	$250.31	$250.30	$250.30
Purchase #2	$12.82	4.452%	$13.3907	$13.39	$13.40	$13.40
Purchase #3	$146.35	6.229%	$155.4661	$155.47	$155.45	$155.50
Purchase #4	$171.41	11.534%	$191.1804	$191.18	$191.20	$191.20
Purchase #5	$37.81	8.381%	$40.9789	$40.98	$41.00	$41.00
Purchase #6	$198.69	3.336%	$205.3183	$205.32	$205.30	$205.30
Purchase #7	$209.91	12.226%	$235.5736	$235.57	$235.55	$235.60
7 purchase totals =	$1,013.55		$1,092.2216	$1,092.22	$1,092.20	$1,092.30