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	$162.37	3.404%	$167.8971	$167.90	$167.90	$167.90
Purchase #2	$85.57	13.646%	$97.2469	$97.25	$97.25	$97.20
Purchase #3	$95.46	9.608%	$104.6318	$104.63	$104.65	$104.60
Purchase #4	$203.50	3.102%	$209.8126	$209.81	$209.80	$209.80
Purchase #5	$173.33	10.426%	$191.4014	$191.40	$191.40	$191.40
Purchase #6	$138.39	10.381%	$152.7563	$152.76	$152.75	$152.80
Purchase #7	$91.69	8.110%	$99.1261	$99.13	$99.15	$99.10
7 purchase totals =	$950.31		$1,022.8722	$1,022.88	$1,022.90	$1,022.80