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	$185.28	3.539%	$191.8371	$191.84	$191.85	$191.80
Purchase #2	$186.73	5.319%	$196.6622	$196.66	$196.65	$196.70
Purchase #3	$104.63	5.386%	$110.2654	$110.27	$110.25	$110.30
Purchase #4	$229.37	4.686%	$240.1183	$240.12	$240.10	$240.10
Purchase #5	$130.76	8.838%	$142.3166	$142.32	$142.30	$142.30
Purchase #6	$210.32	13.527%	$238.77	$238.77	$238.75	$238.80
Purchase #7	$242.93	8.435%	$263.4211	$263.42	$263.40	$263.40
7 purchase totals =	$1,290.02		$1,383.3907	$1,383.40	$1,383.30	$1,383.40