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	$48.45	10.554%	$53.5634	$53.56	$53.55	$53.60
Purchase #2	$182.36	3.316%	$188.4071	$188.41	$188.40	$188.40
Purchase #3	$96.30	3.756%	$99.917	$99.92	$99.90	$99.90
Purchase #4	$116.89	7.265%	$125.3821	$125.38	$125.40	$125.40
Purchase #5	$133.29	4.838%	$139.7386	$139.74	$139.75	$139.70
Purchase #6	$36.55	11.270%	$40.6692	$40.67	$40.65	$40.70
Purchase #7	$160.32	9.563%	$175.6514	$175.65	$175.65	$175.70
7 purchase totals =	$774.16		$823.3288	$823.33	$823.30	$823.40