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	$178.80	3.736%	$185.48	$185.48	$185.50	$185.50
Purchase #2	$195.31	7.669%	$210.2883	$210.29	$210.30	$210.30
Purchase #3	$89.56	3.578%	$92.7645	$92.76	$92.75	$92.80
Purchase #4	$209.51	4.371%	$218.6677	$218.67	$218.65	$218.70
Purchase #5	$59.53	12.661%	$67.0671	$67.07	$67.05	$67.10
Purchase #6	$80.52	5.732%	$85.1354	$85.14	$85.15	$85.10
Purchase #7	$64.38	8.373%	$69.7705	$69.77	$69.75	$69.80
7 purchase totals =	$877.61		$929.1735	$929.18	$929.15	$929.30