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	$179.67	6.211%	$190.8293	$190.83	$190.85	$190.80
Purchase #2	$191.56	4.531%	$200.2396	$200.24	$200.25	$200.20
Purchase #3	$236.79	3.415%	$244.8764	$244.88	$244.90	$244.90
Purchase #4	$218.96	9.816%	$240.4531	$240.45	$240.45	$240.50
Purchase #5	$76.74	12.360%	$86.2251	$86.23	$86.25	$86.20
Purchase #6	$168.82	9.766%	$185.307	$185.31	$185.30	$185.30
Purchase #7	$206.69	8.742%	$224.7588	$224.76	$224.75	$224.80
7 purchase totals =	$1,279.23		$1,372.6893	$1,372.70	$1,372.75	$1,372.70