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	$188.83	5.702%	$199.5971	$199.60	$199.60	$199.60
Purchase #2	$100.50	7.769%	$108.3078	$108.31	$108.30	$108.30
Purchase #3	$69.58	5.495%	$73.4034	$73.40	$73.40	$73.40
Purchase #4	$181.54	8.144%	$196.3246	$196.32	$196.30	$196.30
Purchase #5	$163.58	10.363%	$180.5318	$180.53	$180.55	$180.50
Purchase #6	$141.50	8.436%	$153.4369	$153.44	$153.45	$153.40
Purchase #7	$102.77	6.360%	$109.3062	$109.31	$109.30	$109.30
7 purchase totals =	$948.30		$1,020.9078	$1,020.91	$1,020.90	$1,020.80