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	$175.85	5.745%	$185.9526	$185.95	$185.95	$186.00
Purchase #2	$156.56	6.614%	$166.9149	$166.91	$166.90	$166.90
Purchase #3	$42.57	8.473%	$46.177	$46.18	$46.20	$46.20
Purchase #4	$86.42	7.370%	$92.7892	$92.79	$92.80	$92.80
Purchase #5	$149.84	10.553%	$165.6526	$165.65	$165.65	$165.70
Purchase #6	$55.69	7.603%	$59.9241	$59.92	$59.90	$59.90
Purchase #7	$84.71	12.372%	$95.1903	$95.19	$95.20	$95.20
7 purchase totals =	$751.64		$812.6007	$812.59	$812.60	$812.70