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	$168.56	4.840%	$176.7183	$176.72	$176.70	$176.70
Purchase #2	$100.76	3.534%	$104.3209	$104.32	$104.30	$104.30
Purchase #3	$72.79	13.279%	$82.4558	$82.46	$82.45	$82.50
Purchase #4	$74.26	7.175%	$79.5882	$79.59	$79.60	$79.60
Purchase #5	$195.66	8.658%	$212.6002	$212.60	$212.60	$212.60
Purchase #6	$165.51	7.822%	$178.4562	$178.46	$178.45	$178.50
Purchase #7	$50.88	6.471%	$54.1724	$54.17	$54.15	$54.20
7 purchase totals =	$828.42		$888.3120	$888.32	$888.25	$888.40