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	$124.59	5.195%	$131.0625	$131.06	$131.05	$131.10
Purchase #2	$229.30	4.830%	$240.3752	$240.38	$240.40	$240.40
Purchase #3	$113.33	6.112%	$120.2567	$120.26	$120.25	$120.30
Purchase #4	$79.75	13.415%	$90.4485	$90.45	$90.45	$90.40
Purchase #5	$209.72	4.641%	$219.4531	$219.45	$219.45	$219.50
Purchase #6	$54.95	6.703%	$58.6333	$58.63	$58.65	$58.60
Purchase #7	$38.74	11.288%	$43.113	$43.11	$43.10	$43.10
7 purchase totals =	$850.38		$903.3423	$903.34	$903.35	$903.40