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	$72.72	7.413%	$78.1107	$78.11	$78.10	$78.10
Purchase #2	$81.31	6.346%	$86.4699	$86.47	$86.45	$86.50
Purchase #3	$76.54	5.669%	$80.8791	$80.88	$80.90	$80.90
Purchase #4	$77.82	12.627%	$87.6463	$87.65	$87.65	$87.60
Purchase #5	$84.66	8.581%	$91.9247	$91.92	$91.90	$91.90
Purchase #6	$242.42	8.866%	$263.913	$263.91	$263.90	$263.90
Purchase #7	$47.83	13.583%	$54.3267	$54.33	$54.35	$54.30
7 purchase totals =	$683.30		$743.2704	$743.27	$743.25	$743.20