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	$145.35	11.783%	$162.4766	$162.48	$162.50	$162.50
Purchase #2	$149.76	12.844%	$168.9952	$169.00	$169.00	$169.00
Purchase #3	$70.48	12.251%	$79.1145	$79.11	$79.10	$79.10
Purchase #4	$31.32	4.850%	$32.839	$32.84	$32.85	$32.80
Purchase #5	$107.82	3.741%	$111.8535	$111.85	$111.85	$111.90
Purchase #6	$107.54	9.199%	$117.4326	$117.43	$117.45	$117.40
Purchase #7	$104.59	5.455%	$110.2954	$110.30	$110.30	$110.30
7 purchase totals =	$716.86		$783.0068	$783.01	$783.05	$783.00