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	$156.99	13.348%	$177.945	$177.95	$177.95	$177.90
Purchase #2	$89.42	8.299%	$96.841	$96.84	$96.85	$96.80
Purchase #3	$94.50	4.761%	$98.9991	$99.00	$99.00	$99.00
Purchase #4	$141.51	13.251%	$160.2615	$160.26	$160.25	$160.30
Purchase #5	$219.51	6.316%	$233.3743	$233.37	$233.35	$233.40
Purchase #6	$71.87	7.344%	$77.1481	$77.15	$77.15	$77.10
Purchase #7	$162.91	5.423%	$171.7446	$171.74	$171.75	$171.70
7 purchase totals =	$936.71		$1,016.3136	$1,016.31	$1,016.30	$1,016.20