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	$98.49	10.794%	$109.121	$109.12	$109.10	$109.10
Purchase #2	$62.98	4.518%	$65.8254	$65.83	$65.85	$65.80
Purchase #3	$150.79	10.664%	$166.8702	$166.87	$166.85	$166.90
Purchase #4	$159.27	10.392%	$175.8213	$175.82	$175.80	$175.80
Purchase #5	$167.50	9.797%	$183.91	$183.91	$183.90	$183.90
Purchase #6	$188.31	3.474%	$194.8519	$194.85	$194.85	$194.90
Purchase #7	$135.83	6.420%	$144.5503	$144.55	$144.55	$144.60
7 purchase totals =	$963.17		$1,040.9501	$1,040.95	$1,040.90	$1,041.00