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	$174.58	7.753%	$188.1152	$188.12	$188.10	$188.10
Purchase #2	$62.84	3.613%	$65.1104	$65.11	$65.10	$65.10
Purchase #3	$90.31	13.660%	$102.6463	$102.65	$102.65	$102.60
Purchase #4	$183.42	3.524%	$189.8837	$189.88	$189.90	$189.90
Purchase #5	$182.80	4.225%	$190.5233	$190.52	$190.50	$190.50
Purchase #6	$232.74	12.578%	$262.014	$262.01	$262.00	$262.00
Purchase #7	$35.78	3.822%	$37.1475	$37.15	$37.15	$37.10
7 purchase totals =	$962.47		$1,035.4404	$1,035.44	$1,035.40	$1,035.30