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	$129.96	10.483%	$143.5837	$143.58	$143.60	$143.60
Purchase #2	$101.48	8.637%	$110.2448	$110.24	$110.25	$110.20
Purchase #3	$83.63	3.301%	$86.3906	$86.39	$86.40	$86.40
Purchase #4	$18.82	8.367%	$20.3947	$20.39	$20.40	$20.40
Purchase #5	$250.59	12.836%	$282.7557	$282.76	$282.75	$282.80
Purchase #6	$225.51	6.820%	$240.8898	$240.89	$240.90	$240.90
Purchase #7	$189.55	11.487%	$211.3236	$211.32	$211.30	$211.30
7 purchase totals =	$999.54		$1,095.5829	$1,095.57	$1,095.60	$1,095.60