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	$243.34	5.493%	$256.7067	$256.71	$256.70	$256.70
Purchase #2	$149.69	8.517%	$162.4391	$162.44	$162.45	$162.40
Purchase #3	$199.69	5.782%	$211.2361	$211.24	$211.25	$211.20
Purchase #4	$88.96	12.473%	$100.056	$100.06	$100.05	$100.10
Purchase #5	$103.73	10.331%	$114.4463	$114.45	$114.45	$114.40
Purchase #6	$196.69	3.161%	$202.9074	$202.91	$202.90	$202.90
Purchase #7	$95.82	9.164%	$104.6009	$104.60	$104.60	$104.60
7 purchase totals =	$1,077.92		$1,152.3925	$1,152.41	$1,152.40	$1,152.30