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	$188.59	8.817%	$205.218	$205.22	$205.20	$205.20
Purchase #2	$81.67	8.150%	$88.3261	$88.33	$88.35	$88.30
Purchase #3	$132.65	6.623%	$141.4354	$141.44	$141.45	$141.40
Purchase #4	$94.65	11.848%	$105.8641	$105.86	$105.85	$105.90
Purchase #5	$207.98	7.579%	$223.7428	$223.74	$223.75	$223.70
Purchase #6	$64.56	11.861%	$72.2175	$72.22	$72.20	$72.20
Purchase #7	$53.75	6.216%	$57.0911	$57.09	$57.10	$57.10
7 purchase totals =	$823.85		$893.8950	$893.90	$893.90	$893.80