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	$177.25	9.822%	$194.6595	$194.66	$194.65	$194.70
Purchase #2	$188.64	5.814%	$199.6075	$199.61	$199.60	$199.60
Purchase #3	$174.98	11.779%	$195.5909	$195.59	$195.60	$195.60
Purchase #4	$28.33	3.695%	$29.3768	$29.38	$29.40	$29.40
Purchase #5	$150.39	6.212%	$159.7322	$159.73	$159.75	$159.70
Purchase #6	$228.91	9.502%	$250.661	$250.66	$250.65	$250.70
Purchase #7	$66.40	6.328%	$70.6018	$70.60	$70.60	$70.60
7 purchase totals =	$1,014.90		$1,100.2297	$1,100.23	$1,100.25	$1,100.30