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	$99.53	9.735%	$109.2192	$109.22	$109.20	$109.20
Purchase #2	$98.68	6.721%	$105.3123	$105.31	$105.30	$105.30
Purchase #3	$249.68	5.586%	$263.6271	$263.63	$263.65	$263.60
Purchase #4	$102.61	11.662%	$114.5764	$114.58	$114.60	$114.60
Purchase #5	$195.34	7.250%	$209.5022	$209.50	$209.50	$209.50
Purchase #6	$67.25	9.452%	$73.6065	$73.61	$73.60	$73.60
Purchase #7	$150.86	3.600%	$156.291	$156.29	$156.30	$156.30
7 purchase totals =	$963.95		$1,032.1347	$1,032.14	$1,032.15	$1,032.10