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	$101.41	8.312%	$109.8392	$109.84	$109.85	$109.80
Purchase #2	$72.39	7.799%	$78.0357	$78.04	$78.05	$78.00
Purchase #3	$90.63	11.548%	$101.096	$101.10	$101.10	$101.10
Purchase #4	$156.96	5.415%	$165.4594	$165.46	$165.45	$165.50
Purchase #5	$89.25	8.482%	$96.8202	$96.82	$96.80	$96.80
Purchase #6	$191.59	6.808%	$204.6334	$204.63	$204.65	$204.60
Purchase #7	$30.33	8.648%	$32.9529	$32.95	$32.95	$33.00
7 purchase totals =	$732.56		$788.8368	$788.84	$788.85	$788.80