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	$38.33	7.371%	$41.1553	$41.16	$41.15	$41.20
Purchase #2	$168.31	7.653%	$181.1908	$181.19	$181.20	$181.20
Purchase #3	$196.58	7.427%	$211.18	$211.18	$211.20	$211.20
Purchase #4	$211.54	10.802%	$234.3906	$234.39	$234.40	$234.40
Purchase #5	$100.69	8.549%	$109.298	$109.30	$109.30	$109.30
Purchase #6	$183.54	6.570%	$195.5986	$195.60	$195.60	$195.60
Purchase #7	$85.43	9.572%	$93.6074	$93.61	$93.60	$93.60
7 purchase totals =	$984.42		$1,066.4207	$1,066.43	$1,066.45	$1,066.50