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	$182.89	9.523%	$200.3066	$200.31	$200.30	$200.30
Purchase #2	$81.44	8.614%	$88.4552	$88.46	$88.45	$88.50
Purchase #3	$191.25	9.591%	$209.5928	$209.59	$209.60	$209.60
Purchase #4	$226.50	4.159%	$235.9201	$235.92	$235.90	$235.90
Purchase #5	$249.35	8.218%	$269.8416	$269.84	$269.85	$269.80
Purchase #6	$128.64	4.677%	$134.6565	$134.66	$134.65	$134.70
Purchase #7	$81.98	3.830%	$85.1198	$85.12	$85.10	$85.10
7 purchase totals =	$1,142.05		$1,223.8926	$1,223.90	$1,223.85	$1,223.90